The present invention relates to a multi layered wound dressing particularly, but not exclusively, for use as a dressing on infected wounds and especially malodorous wounds such as infected ulcers.
Alginate fabrics have, in conjunction with charcoal cloth been used in wound dressings for malodorous wounds and examples of such commercially available dressings are sold under the trade marks KALTOCARB, ACTISORB PLUS and LYOFOAM C. A dressing available under the trade mark KALTOCARB comprises a non-woven alginate pad and charcoal cloth fused together with a polyamide net; a dressing available under the trade mark ACTISORB PLUS comprises charcoal cloth together with silver sealed within a nylon sleeve and may further include one or more absorbent layers; a dressing available under the trade mark LYOFOAM C includes viscose fibres treated with activated charcoal encapsulated by a layer of polyurethane foam.
EP 0099758 describes a composite wound dressing which can include alginate fabric used in conjunction with charcoal cloth. This wound dressing comprises a semipermeable membrane, which may comprise alginate, a supporting layer such as charcoal cloth and a biodegradable tissue interface such as sodium-calcium alginate. The supporting layer is located between the semi-permeable membrane and the biodegradable tissue interface.
GB 2228682 and GB 2290031 describe wound dressings which may include and odour adsorbing layer and have as their absorbent layer a layer or layers of foam. Neither document discloses the use of a fibrous absorbent layer in combination with an odour adsorbing layer.
EP 0026572 concerns a multilayered wound dressing which includes a layer of curative and absorbent material comprising a blend of one or more water soluble or swellable hydrocolloids and a binder which layer contacts the wound, an intermediate layer of deodorising material and an air and gas permeable layer which secures the dressing to the body. The curative and absorbent material is a homogeneous cohesive mass which is punched with holes so as not to impede the passage of gas away from the wound. A liquid impermeable material such as a non-woven fabric may be included in the dressing between the wound contacting layer and the deodorising layer.
A problem associated with known multi-layered dressings which employ charcoal cloth is that the dressing is a relatively rigid structure. This is a disadvantage since malodorous wounds tend to be sited in areas such as the neck or underarm where a highly conformable dressing is needed. In addition the wound contact layer tends to be somewhat hard which can cause discomfort to the patient especially when the dressing is changed.
Furthermore, malodorous wounds tend to be wounds that generate high levels of exudate. This leads not only to the problem of leakage of wound exudate but also, it is believed, limits the ability of the charcoal to adsorb malodours due to saturation.
We have now developed a multi layered wound dressing which alleviates the above problems and there is provided by the present invention a multi layered dressing comprising a
fibrous absorbent layer for absorbing wound exudate, a barrier layer and an odour adsorbing layer where said barrier layer is located between the absorbent layer and the odour adsorbing layer.
In use the dressing may be oriented so that the absorbent layer is closest to the wound and preferably so that the absorbent layer contacts the wound and surrounding skin.
The absorbent layer is fibrous and can comprise any biodegradable fibre. Preferred fibres for use in the absorbent layer of the present invention include those of alginate, viscose, modified cellulose, cellulose, polyester, polypropylene and co-polymers thereof, pectin, chitosan fibres, hyaluronic acid fibres or other polysaccharide fibres or fibres derived from gums. Most preferred are highly absorbent fibres such as OASIS(trademark) fibre as disclosed in EP 0269393 A, modified cellulose fibres as described in W093/12275 to Courtaulds Plc or GB9301258 to Courtaulds Plc and alginate fibres as described in WO 94/17227 to E. R. Squibb and Sons. By xe2x80x9chighly absorbentxe2x80x9d with-respect to the fibre it is meant that they can absorb at least 25 g/g of deionized water. Most aptly the fibres can absorb at least 60 times, more aptly at least 80 times, for example 80-280 times of their own weight, more aptly 90 to 150 times for example about 120 times of their own weight of deionized water. The fibres for use in the absorbent layer may also be mixed or blended to form a composite layer or may be fibres made of a mixture of any of the above ingredients.
The barrier layer deters the movement of exudate to the odour adsorbing layer while permitting the movement of odour to the odour adsorbing layer. The delay in the movement of exudate imposed by the barrier layer increases the time over which the dressing is able to adsorb odour and increases the quantity of odour adsorbed. The barrier can be of the type known as xe2x80x9cone way wickingxe2x80x9d. This type of material is vacuum perforated over a small cone or micro funnel such that a small hole is formed which allows the movement of odours but deters the movement of exudate away from the absorbent layer. A preferred example is FLEXIFILM, an ethylene vinyl acetate film of the type sold by Tredegar. These films can be made from a range of polymers, for example high density polyethylene, polypropylene, medium density polyethylene, ethylene methyl acetate and ethylene vinyl acetate. Preferred is a film made from 50% EMA, 43% EVA and balance white colourant.
Alternatively the barrier layer can be a non-woven cloth that is impermeable to liquids but gas permeable. It is believed that the advantage of retaining the exudate in the absorbent layer and detering it from moving immediately into the odour adsorbing layer is that the maximum free surface area for odour adsorption is retained and therefore the dressing maintains its odour adsorbing properties for longer.
The odour adsorbing layer is preferably a charcoal cloth such as that manufactured by The Charcoal Cloth Company at 120 gsm. The odour adsorbing layer may also be charcoal coated material such as that made by Lantor.